This invention relates to an improved hypodermic syringe.
A typical syringe includes a barrel having a discharge orifice at its front end and defining a bore through which a plunger extends and travels. The plunger typically carries a piston which sweeps a portion of the bore so as to draw in fluid on the intake stroke (pull-back of the plunger) and to discharge fluid on the discharge stroke (push-in of the plunger). Many syringes are pre-filled and no intake stroke is required by the operator.
Although syringes are generally packaged in a sterile manner, once the syringe is removed from its package contamination of the bore may occur. Typically such contamination might occur by contaminants entering the bore from the rear thereof. During the intake stroke, the piston ring may communicate with the contaminant and on the discharge stroke, the contaminant may be brought forward by the piston ring and communicated with the fluid medicament being discharged.
It is, therefore, an object of the present invention, to provide a syringe having means to prevent fluid medicament from communicating with the rearward, possibly contaminated portion of the syringe's barrel.
A further object of the present invention is to provide a syringe that is simple in construction and efficient to manufacture.
Another object of the present invention is to provide a syringe having a pair of axially spaced pistons with the chamber defined by the pistons being prevented from communicating with the area forward of the forward piston.
A further object of the present invention is to provide a syringe that is usable with an infusion pump, that is simple in construction and has means for effectively segregating the front portion of the bore from the rear portion thereof.
Other objects and advantages of the present invention will become apparent as the description proceeds.